A two-part curing polyurethane elastomer composition has excellent physical properties of a cured product, such as strength, elongation, elastic modulus and the like, and therefore is widely used in applications such as a water-proof material, a floor material, a pavement material, an adhesive, a sealing material and the like. The two-part curing polyurethane elastomer composition is cured by stirring and mixing a curing agent comprising an active hydrogen-containing compound as a main component and a base resin comprising a polyisocyanate component as a main component, and executing with a trowel, a spatula, a roller or the like, or casting in a mold. Therefore, where the viscosity after two-part mixing is high, bubbles are liable to be included when executing with a trowel, a spatula, a roller or the like, resulting in deterioration of appearance and performance. Further, where casting in a mold, inclusion of bubbles is large, and casting workability deteriorates such that fine spaces cannot be filled with a composition.
Conventionally, a production method of a two-part curing polyurethane elastomer composition comprising an active hydrogen-containing compound and a polyisocyanate component is generally a prepolymer method using an isocyanate-terminated urethane polymer obtained by reacting an organic polyisocyanate and a polyol with an equivalent ratio of an isocyanate group to an active hydrogen group being 2.0 or less. Other methods are a semi-one shot method using a partial prepolymer obtained by reacting an organic polyisocyanate as a polyisocyanate component and a polyol with an equivalent ratio of an isocyanate group to an active hydrogen group exceeding 2.0, and a one shot method using an organic polyisocyanate alone.
Examples of the active hydrogen-containing compound to be reacted with the polyisocyanate component include a polyether polyol such as a polytetramethylene ether glycol obtained by ring opening polymerization of tetrahydrofuran, and a polyoxyalkylene polyol obtained by addition polymerizing at least one of alkylene oxides such as ethylene oxide, propylene oxide and butylene oxide, with a polyhydric alcohol such as propylene glycol, dipropylene glycol, glycerin and trimethylol propane; a polyester polyol obtained by condensation polymerization of at least one polyhydric alcohol such as ethylene glycol, propylene glycol, diethylene glycol, butanediol, pentanediol and hexanediol, and at least one of malonic acid, maleic acid, succinic acid, adipic acid, glutaric acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and the like; and a polyester polyol obtained by ring opening polymerization of caprolactone or the like.
However, where a polyether polyol is used as the active hydrogen-containing compound, a cured product has relatively good wet heat resistance, but has poor heat resistance. On the other hand, where a polyester polyol is used, heat resistance is relatively good, but wet heat resistance is poor.
As a method for improving heat resistance and wet heat resistance, it is proposed to use a hydride of a hydroxyl group-containing liquid polyisoprene as the active hydrogen-containing compound (JP-A-63-57626, JP-A-1-203421, JP-A-6-220157, JP-A-7-102033, and the like). However, when the hydride of a hydroxyl group-containing liquid polyisoprene proposed in those patent publications is used, a composition has high viscosity, and when executing with a trowel, a spatula, a roller or the like after two-part mixing, bubbles are liable to be included, resulting in deterioration of appearance and performance. Further, in the case of casting in a mold, there are the disadvantages that inclusion of bubbles is large, and fine spaces cannot be filled with a composition.
The prior art information of this invention is as follows; JP-A-63-57626, JP-A-1-203421, JP-A-6-220157 and JP-A-7-102033.